Process of increasing the molecular weight of molten polyamides with diaryl esters

ABSTRACT

A PROCESS FOR INCREASING THE CHAIN LENGHT AND HENCE THE VISCOSITY OF SYNTHETIC LINEAR POLYAMIDES, WHILST PRESERVING THE LINERITY BY MEANS OF ADDITION OF A DEFINED CLASS OF DIARYL ESTERS. ALSO INCLUDED IN THE INVENTION ARE THE POLYMERS WITH INCREASED VISCOSITY AND SHAPED PRODUCTS MADE THEREFROM.

United States Patent M US. Cl. 260-78 SC 11 Claims ABSTRACT OF THE DISCLOSURE A process for increasing the chain length and hence the viscosity of synthetic linear polyamides, whilst preserving the linearity by means of addition of a defined class of diaryl esters. Also included in the invention are the polymers with increased viscosity and shaped products made therefrom.

The present invention which is a continuation of application Ser. No. 868,057, filed Oct. 21, 1969, now abandoned, relates to the preparation of improved synthetic linear polyamides, including copolyamides, particularly those made from polymerization of dibasic acids and diamines, and more particularly nylon 66. It includes shaped products such as fibres, yarns, films and the like prepared from such improved polymers.

The invention will now be particularly described, in no way limitatively, with reference to the making of improved polymers for melt-spinning into the industrial and textile fibres.

For a number of industrial products, such as for instance tire cord, synthetic linear polyamides having a high relative viscosity (designated hereinafter by R.V.) are required. In general, the higher the R.V. of a polyamide the higher the strength or tenacity of the products prepared from it and such high strength is of great importance in tire cords, for example.

A high R.V. polymer can also be of great importance in the spinning of textile filaments of non-circular cross-section, where a low R.V. polymer tends to lose its shape after leaving the spinnerct.

When the polymers are to be melt spun into, for instance, filaments, it is important that the high R.V. should not be attained by cross-linking, which tends to give a three-dimensional gelled, non-processable product, but should be attained substantially by extension of polymer chain length, so retaining the linear characteristics of the polymer. Such necessity for linearity of the high R.V. polymers for fibre production can be contrasted with the requirement of a high R.V. polymer destined to be used for moulding purposes where cross linking may be desirable.

Many attempts have been made to prepare high R.V. linear polymers which can be spun and drawn to make high strength yarns, but it has been found very ditlicult to preserve polymer linearity.

Applicants have found a class of compounds which are esters, as hereinafter defined, which when added in suitable amounts and under suitable conditions to a polyamide increases the R.V. of said polyamide, substantially by increasing chain length and not by cross-linking, so affording a high R.V. polymer which may be melt spun and drawn to produce products, such as tire cords, with improved strength.

Chain linking can occur via either amine groups or carboxyl groups, situated at the ends of polymer chains. The compounds of the present invention combine preferentially with free amine ends, so eliminating them. The re- 3,810,876 Patented May 14, 1974 sulting low level of amine end groups in the finally prepared polymers confers a surprising improvement in heat resistance on said polymers and on the products made therefrom. Such improved heat resistance is particularly valuable in tire cords since, during the processing which leads to their being incorporated into a tire, they are frequently subjected to high temperatures, which may degrade them.

Since said compounds react preferentially with the amine ends, the concentration of amine ends in the prepared polyamide, prior to addition of the said compounds, will have a considerable effect on the R.V. rise attained, as will, of course, the proportion of the compound added to the polyamide. If necessary, the amine end content of the polyamide prior to addition of said compounds may be increased by addition of excess diamine to the original polymer-forming monomer mixture.

The use of the compounds of the present invention provides a further advantage in that when they react with the molten polyamide substantially no undesirable by-products are formed. There is little or no bubble formation, such as is frequently met with when using, for instance, carbonate or polycarbonate additives with polyamides. Such bubble formation naturally gives rise to considerable difficulties in spinning and, if excessive, can lead to a drawn product having poor strength.

A certain amount of water is present in polymer prepared by polycondensation, even when the reaction is carried out in an inert-gas atmosphere, such as nitrogen. If amine or acid chain linking agents instead of esters are added to polymers so prepared, further water is produced by the linking reaction. Such Water tends to hydrolyze the polymer if said polymer is held at high temperatures, polycondensation being a substantially reversible reaction, and so to reduce its molecular weight and R.V.

It is clear therefore, that during preparation of high R.V. polyamides according to the process of the present invention, if water, from any source, is present two coniiicting reactions occur: chain linking, tending to increase the R.V. and hydrolysis tending to lower the R.V. Applicants have found that because of these conflicting processes there is an optimum point in time, from the moment when the compounds of the present invention are added, where the R.V. reaches a maximum and beyond which point the R.V. starts to fall.

The finding of this optimum point becomes very critical when the spinning process is carried out under steam, as is commonly practiced. Alleviation of the problem of hydrolysis and consequent R.V. decrease is attained by the use of esters, which do not produce hydrolyzing water as a reaction by-product and such esters favor the movement of the reaction towards high R.V. If the presence of an optimum point, as aforesaid, is not appreciated the attainment of the optimum high R.V. by the use of the present invention can, in practice, easily be missed, especially in the presence of steam, that is, in the presence of a large amount of water. For instance, the time to reach the maximum value when nylon 66 polymer is held at 290 C. under steam is only about two minutes after the addition of the esters to the previously prepared polyamide.

In practice the time for reaching the optimum R.V. varies according to process conditions, the type of polymer and the type of additive etc. However, the knowledge that such an optimum time exists is of great value, since such knowledge leads the practicer of the present invention to search for it by simple experimentation and thence to develop optimum process conditions. v

'From what has been said it will be seen thaFthTfiiompounds added to prepared polyamides for producing an increase in R.V. while preserving the linear nature of such polymers should be adequately stable to pyrolysis, react sufficiently rapidly and substantially with the amine end groups only and favor polymerization rather than hydrolysis.

A class of compounds which has been found by extensive experimentation to fulfill the aforesaid stipulations is defined as: diaryl esters, preferably diphenyl esters or polyaryl esters, of dibasic acids with a carbon number of to 36. Said dibasic acids may be aliphatic, cycloaliphatic, aromatic or heterocyclic acids and may optionally contain ether-linked oxygen or sulphur or tertiary nitrogen atoms or keto or amide groups as part of their structure. Specifically excluded from the above class are all dicarboxylic acids with:

1) The carboxyl groups situated on neighboring or vicinal carbon atoms.

(2) Carboxyl groups occuping the peri-positions of structures containing the naphthalene nucleus.

(3) Gem dicarboxyl groups except when the latter are attached to a fully alkylated carbon atom i.e. the grouping shown is excluded except when a and b are both saturated aliphatic groups or form part of a saturated alicyclic structure.

a\ /COOH As examples of dibasic acids further to those quoted in Tables 1, 4 and 6 one may cite:

Pimelic acid Suberic acid Hexadecane 1,16 dicarboxylic acid 2 methylbutane 1:4 dicarboxylic acid 2 ethyl 3 methylbutane 1:4 dicarboxylic acid 1 ethylbutane 1:4 dicarboxylic acid Propane 2:2 dicarboxylic acid Butane 2:2 dicarboxylic acid Cyclopentane 1:1 dicarboxylic acid Hexahydroiso or terephthalic acid Hexahydrohomophthalic acid Hexahydrohomoiso or terephthalic acid 3 carboxy-l cyclopentylacetic acid 3 carboxy 2:2 dimethylcyclobutylacetic acid 2,5-dimethylterephthalic acid 5 tertbuylisophthalic acid Naphthalene 1:4 dicarboxylic acid Naphthalene 2:7 dicarboxylic acid Naphthalene 1:5 diacetic acid Benzophenone 2:4 dicarboxylic acid 3-(ortho or meta or para carboxyphenyl) propionic acid 9,10 di(;3-carboxyethyl) anthracene 2,3,5,6 tetra-methyl-p-phenylene-di-;8-propionic acid 2,5 dimethyl-p-phenylenediacetic acid Di-ortho, meta or para(carboxymethoxy)benzene 2:2 di (la-(carboxymethoxy) phenyl) propane fi-(p-(Carboxymethyl) phenyl) propionic acid Di (p-(carboxymethyl) phenyl) ether Di (p-(carboxymethoxy) phenyl) ether 1:7 di (carboxymethoxy) naphthalene 5 carboxy-4-thiazolylacetic acid 5 carboxybenziminazole-Z-pelargonic acid Furan-2:5 dicarboxylic acid Furan-2z5 di-fi-propionic acid 5 carboxy-2 furan-p-propionic acid Tetra hydro furan-2:5 dicarboxylic acid 2:6 di (carboxymethyl -pyridine.

. Said aryl esters may be obtained from mono or dihydric phenols or naphthols or the bis-condensation products of monohydric phenols or naphthols with carbonyl compounds; all such phenolic structures may optionally carry additional alkyl, cycloal-kyl or aryl substituents. As examples of aryl esters limbs? to those quoted in Table 3 hereinafter, one may cite the adipates from 2 or 4 mono-, or 2,4 di-, ethyl, isopropyl, cyclohexyl or a-methylcyclohexyl phenol.

Dihydric phenols are illustrated by the examples of polyaryl esters in Table 5 hereinafter.

An example of the condensation product of a carbonyl compound with phenol is 4,4 isopropylidene diphenol. Polyaryl esters of this compound are illustrated in Examples 45 to 48 of Table 5. As further examples of carbonyl compounds one may cite formaldehyde, normal or iso butyraldehyde or cyclohexanone, which will phenol give respectively 4,4 methylene, 4,4 normal or iso butylidene, and cyclo hexylidene diphenol.

In addition to resorcinol, shown as Example 49 hereinafter one may cite for example, quinol, 2,7 dihydroxynaphthalene and 4,4 dihydroxy diphenyl.

Accordingly the present invention, in one of its aspects, provides a process for the production of a synthetic linear melt-spinnable polyamide or co-polyamide having increased relative viscosity which process comprises the incorporation into a synthetic linear polyamide or copolyamide in the molten state of at least one diaryl or polyaryl ester of a dicarboxylic acid with a carbon number of 5 to 36 and having the carboxyl groups attached either to a single carbon atom, provided the other bonds of said carbon atom are connected to saturated aliphatic groups or form part of a saturated alicyclic structure, or attached to separate carbon atoms other than vicinalor peri-positioned carbon atoms.

A further aspect of the present invention provides synthetic linear melt-spinnable polyamides having increased relative viscosity, obtained by the aforesaid method.

The ester is preferably added in an amount which is substantially stoichiometrically equivalent to the free polymer amine end groups. However, in practice the amount added should be such, either above or below the stoichiometric equivalent as to accomplish the objects of the invention while keeping undesirable effects at a minimum. The addition may be made, for instance, to the polymer in a polymerizing autoclave, preferably at extrusion from said autoclave, or the ester may be coated onto polymer chip prior to melting and spinning or other shaping process or a concentrate of ester and polyamide or copolyamide, called a master batch, may be made and added to the main polymer batch either in the autoclave or prior to spinning or other shaping process or the ester may be pelletized with the use of an inert binder and the pellets subsequently blended with polymer chips. Alternatively the compound may be added, either alone or in admixture, to the polymer melt just prior to spinning or other shaping process, for instance in a continuous polymerization process. Other methods of addition may be devised to meet particular requirements. Other additives may be present in the polymer, such as pigments stabilizers and the like, so long as these do not vitiate objects of the invention. Of course, if found desirable, a mixture of two or more esters of the present invention may be used.

The present invention is illustrated but not limited by the following examples.

Characteristics mentioned in the examples are defined and measured as follows:

(1) Relative viscosity (R.V.).-The relative viscosity of a polyamide is defined as the ratio of the viscosity of a solution of given strength of the polyamide in a given solvent to the viscosity of the solvent itself at the same prescribed temperature. In the case of the relative viscosity values quoted in this specification the solvent employed was a by weight (solutezsolution) aqueous solution of formic acid. The viscosity of an 8.4% by weight (solutezsolution) solution of the polyamide in the above mentioned solvent was determined and the ratio of said viscosity to the viscosity of the solvent itself evaluated. The temperature employed for the determination of viscosities was 25 C.

(2) Heat strength retention (H.S.R.).A suitable length of the yarn was heated in air in an oven at 225 C. for 30 mins. Its tenacity was then measured and expressed as a percentage of the tenacity of the yarn before heating.

Other characteristics are measured by the conventional methods (tenacity is measured on an Instron instrument). The terms A.E.G. and C.E.G. in the following examples denote micro-equivalents of amine or carboxyl groups respectively, per gram of polymer (or equivalents per grams of polymer).

The inherent viscosity (abbreviated I.V. in the tables) of a polyamide is defined herein as twice the natural logarithm of the quotient of the viscosity at 25 C. of a solution of a 0.5 percent weight by volume of the polyamide dissolved in the appropriate solvent divided by the viscosity of the said solvent at the same temperature. The viscosity measurements are carried out in an Ostwald type viscometer.

The solvent used was 90% aqueous phenol in all cases except Examples 66 and 70, where the solvent was mcresol and Example 73 where the solvent was dichloroacetic acid.

EXAMPLES 1-18 To samples of nylon 66 having various amine end contents and various R.V.s various dibasic esters were added and the mixtures stirred under nitrogen, at 285 C. for various times.

At the end of the given time the molten polymer was allowed to cool to room temperature and the solid polymer mass then broken up. The R.V.s, C.E.Gs and A.E.Gs of these polymers were measured in the usual manner. The results obtained are shown in Table 1.

It can be seen that in all cases where esters falling within the scope of the invention were used, i.e. Examples l-9 inclusive, Example 12 and Examples 14-18 inclusive, the free amine groups of the polymers were greatly reduced.

It can also be seen in Examples 1-4 that the polymer R.V. increased as the concentration of ester in the polymer was increased to that which is the stoichiometric equivalent for the amine ends of the polymer. Furthermore, Examples 14-18 show that if the concentration of ester is increased to values which are substantially in excess of that which is the stoichiometric equivalent for the amine ends of the polymer, there is a tendency to a progressive lowering of the final polymer R.V. The percentage excess in Examples 14-18 refers to the excess of ester over the stoichiometric equivalent for the amine ends of the polymer. The results illustrate that there is an optimum con- ;grntration of additive for obtaining maximum polymer By contrast, Example 13 shows that diphenyl oxalate (carbon number 2) is ineffective for the practice of the invention owing to decomposition at the operating temperature. Examples 10 and 11 show the ineffectiveness of the aliphatic esters in that no practically useful increase in the polymer R.V. is obtained.

EXAMPLES 19-26 A further series of experiments were carried out, similar to those of Examples 1-18, but in this case the polymers obtained were melt-spun and drawn to produce textile yarns. The results obtained are shown in Table 2.

The value TE* shown in Table 2 is a practically convenient parameter for indicating yarn quality. It can be seen that the value of TE tends to fall after the amount 35 of ester exceeds the stoichiometric equivalent.

TABLE 1.6.6 NYLONANALYSES OF POLYMERS STIRRED AT 285 0. WITH ESTERS R.V. 0! Amount Stirring original time at Analysis 6.6 Wt. Equiv. 285 C. Ex. polymer Ester percent per 10 g. in mins. R.V. A.E.G. C.E.G.

1 25 N11 25 160 23 2 25 Dlphenyl ester of deca- 1. 6 80 77 83 22 meiahylene dicarboxyllc ac do 2.4 120 15 160 49 24 25 do 3.0 160 '5 237 33 35 Nil 35 107 35 Diphenyl ester of deea- 2 107 15 116 28 36 meiaghylene diearboxylie ac 35 Diphenyl sebacate 1. 9 107 15 171 12 43 35 Diphenyl terephthalate. 1. 7 107 15 125 17 35 Diphenyl isophthalate 1. 7 107 15 112 12 61 35 Dimethyl terephthalate 1. 1 107 15 40 61 35 Dimethyl isophthalate 1. 1 107 15 40 57 72 35 Diphenyl adipate 1. 6 107 15 162 18 40 35 do 1.3 107 15 Deeomposed 44 NH 44 51 69 44 Diphenyl adipate 0.79 51 i 2 g: 44 ......do 0. s9 1 s7 g 1; Z; 5 54 15 88 44 do 1.0 a a4 15 57 15 85 44 ...-.d0 1.17 1 76 g 3g 1 Too viscous to stir. i 12.5% excess. '25? excess. I 50 a excess.

TABLE 2 Quantity of diphenyl Yarn properties adipate Polymer, (equiv. per Ten. Ext. E

A.E. 10 g.) R.V. (T) (g./d.) (percent) TE l, A.E.G. C.E.G

Example number:

EXAMPLES 21 AND 28 Example 27.-The polymer used in this example, which illustrates the preparation of high tenacity industrial yarn, had the following properties and contained the following additives:

A.E.G.51 C.E.G.68' R.V.-46

Cu60 p.p.m. as cupric acetate, B-22 p.p.m. as NaBO I600 p.p.m. as potassium iodide.

This polymer was coated by tumbling in a Gardner mixer with 0.74% w./w. of a fine crystalline powder of diphenyl adipate, calculated to give equivalent quantities of phenyl ester and amine ends. The coated polymer was then spun under steam at 35 lb./hr. via a melt-pool feeding two filter-packs and spinnerets, at 956 f.p.m. (feet per minute) to produce 4100 denier 140 filament yarn. The resultant undrawn yarn was then drawn at 1100 f.p.m. at a ratio of 5.4 on a drawtwister. The resultant yarn had the following properties.

This polymer was then made into chips and chip coated with diphenyl adipate at 1.03% w./w., which was in stoichiometric equivalence with the free polymer amine ends. The chip coated polymer was then spun and drawn as in Example 27 above to give yarn with the following properties:

Again, the R.V. fell to 64 when only one pack was used for spinning i.e. when the reaction time was increased.

EXAMPLES 29-36 Further examples of the R.V. rise which may be obtained using compounds of the present invention based on Yarn containing adipic acid are illustrated in Table 3 below.

tifgg Nylon 66 polymer was stirred for 15 minutes at 285 4 C., with a diaryl ester of adipic acid. The amount of the 5 1 compound added, the final R.V. of the polymer, as well as g its amine and carboxyl equivalent groups are shown in j 1 Table 3. The results obtained with no compound added 2; to the polymer are shown for comparison in unnumbered 30 examples.

TABLE 3 66 Nylon-analysis oi polymer stirred for 15 mins. at 285 C. with diaryl esters Diaryl esters oi adipic acid- Amount Analysis Wt. Equiv. Example Ester percent per 10' g. R.V. A.E.G. C.E.G

None 107 29 Di p-tert butyl phenyl adipate 2. 2 107 204 12 39 30.. Di p-tert octyl phenyl adipate. 2. 8 107 185 11 42 a1 2.4 107 131 11 46 3.0 107 120 31 55 1.9 107 185 12 a7 2.8 107 175 14 34 1.8 107 132 15 58 2.1 107 105 21 55 With one pack not spinning i.e. at half throughput, the polymer-ester mixture remaining at high temperature for roughly twice the time, the R.V. fell to 54, indicating the large rate dependence of this reaction.

Example 28.-A modified polymer was used; it was normal except that extra hexamethylene diamine was added to a larger production autoclave to give the following properties:

EXAMPLES 37-44 The procedure of Examples 29-36 was repeated, but using in this case diphenyl esters of other dicarboxylic acids.

The results obtained are shown in Table 4. Example 37 shows the unsuitability of a diaryl ester of a dicarboxylic acid with vicinal carboxyl groups.

A.E.G.67 C.E.G.50 R.V.-45

TABLE 4 06 nylon-analysis of polymer stirred for 15 mine. at 285 C. with diaryl esters Diaryl esters of adipic acid- Amount Analysis W Equiv. Example Ester percent per 10' g. R.V. A.E.G. C.E.G.

None. 1 35 107 40 37 Diphenyl succinate 1. 4 107 47 42 32 Diphenyl glutarate. 1. 5 107 61 46 39 3 Diphenyl azelate- 1.8 107 173 15 34 40 Diphenyl ester of Cu di-acid (Empol Dimer 3. 88 107 19 Acid Ex Unilever-Emery N. V. Holland) a trade name. 41 Diphenyl 9,9 fluorene dipropionate 2. 5 107 129 17 46 42. Diphenyll ester of 11,113 trlmethyl-B-p-carboxy 2.5 107 191 11 42 hen -5-carboxy n ane. 43 121 ;119:121 cyclohexane 1,3 dlearboxylate (cls 1.7 107 31 45 isomer 44 Di henyl cyclohexane 1,4 dicarboxylate- Mainly cis isomer 1. 7 107 87 24 36 Mainly trans isomer l. 7 107 133 13 31 3,810,876 9 10 EXAMPLES 45-61 of other esters of the present invention. Said results are These examples illustrate the results from the addition given in Tables -7 below.

TABLE 5 66 nylon-analysis polymers stirred at 285 C. with polyaryl esters Polyaryl ester Amount Vicat soit- Equiv. Analysis ening Wt. per Example Name LV. point percent g. R.V. A.E.G. O.E.G

Nmm 35 107 '40 45 Po1y[2,2 propanebis(4 phenyl adipatefl 0.02 65 1. 8 107 203 13 38 46.- P01y[2,2 propanebis(4 phenyl azelate)] 0.2 2 107 280 8 34 45 Po1y[2,2 propane bis (4-phenyl iso-phthalate 00- 0.25 193 2 107 141 15 39 terephthalate 50/50)]. 48 Poly[2,2 propane bis (4-phenyl iso-phthalate 00- 0. 263 1.3 70 102 58 28 terephthalate 75/25)]. 49 Polsylizglphenylene isophthalate coterephthalate 0.23 156 1.3 107 206 11 40 1 Softens at room temperature.

TAB LE 6 66 nylon-analysis of polymers stirred at 285 C. with diaryl esters from dicarboxylic acids containing ether, tertiary nitrogen, keto and thio groups Amount Analysis Wt. Equiv. Example Dipheuyl ester percent per 10 g. R.V. A.E.G. (LE. G.

N 107 Diphenyl diglyeollate 1. 5 107 88 23 23 Diphenyl oxydibutyrate 1. 8 107 81 34 52 Diphenyl ester of 1:4 bis [p-(beta earboxy 2.9 107 103 24 53 ethyl) phenoxy] butane. 46 53 Diphenyl ester of N N dl(3-carboxy-n- 2.2 107 78 114 19 propyDpiperazine. 54 Diphenyl pyridine 2,6 diearboxylate... 1. 7 107 86 36 27 55 Diphenyl pyridine 2,5 dicarboxylate... 1. 7 107 38 38 56 Diphenyl ester of NN di keto piperazine 2.0 107 78 36 57 diacetie acid. 57 Diphenyl ester of gamma keto pimelic acid" 1. 107 83 31 53 58 Diphenyl ester of thiodipropionic acid 1. 76 107 84 38 1 Example 53. The high value for the amine equivalents in this chain extended polyamide is due to the basic tertiary nitrogen groups introduced by the diphenyl ester.

TABLE 7 66 nylon-analysis of polymer stirred for 15 mine. at 285 C. with mixed phenyi esters of dicarboxylic acids or with a diphenyl ester of a 66 nylon type oligomer Amount, Analysis in Equiv. Example Ester per 10 g. R.V. A.E.G. C.E.G.

gone d 55%- 35 107 40 i hen la inate 59 8 31a y 9e 21 4s ii l m a1 1 a b 11 a l i eny ester 0 ecame y ene icar oxy c aei a l: 84 2s 50 Diphenyl ester of terephthalic acid 53. 5 61 Didpihenyl ester of bis-wcarboxyvaleryl hexamethylene 107 62 58 37 amine.

3,810,876 1 1 1 2 Example 61.-Structural formula of the ester is: The RV. of the control polymer fell quickly with residence time due to hydrolysis. Both the 50 and 65 A.E.G. C6H5OCO(CH2)4CONH(CH2) 6NHCO(CH2)4COOC6H5 chip-coated polymers showed immediate increases in RV.

EXAMPLES 62-70 to 68 and 87 RV. respectively at about 50 secs. but hy- Table 8 shows the viscosity increase obtained using drolysis at longer residence times again caused the RV.

esters of the present invention in admixture with homoto fall h EXAMPLE 77 polymers other than nylon 66. In some cases t e viscosity 15 shown in terms of I.V. instead of R.V., measured as A 0011 polymerizer as described in British patent specidescribed hereinbefore. fication No. 1,042,228 was used to produce 7.25 kg./hr.

TABLE 8 Homopolyamides other than 6.6 stirred at 285 C. with diphenyl esters [or 15 ruins.

Analysis Amount, equiv. Example Polyamlde Diphenyl ester per g. (R V A.E G

62 Polyhexamethylene sebacamide {None 0. 63 104 I Diphenyl sebaca 104 1. 18 63 Polyhexamethylene dodecanedioamide None 0.88 56 Diphenyl decamethylene dicarboxylate 56 1. 01 12 64 None 0.86 98 "lPolydodecamethylene adipamide Diphenyl adipate. 98 1.33 20 Diphenyl decamethylene dicarboxylate... 98 1. 39 22 66 Polyamide from 70% trans trans isomer of his (4 None 0. 50 54 amino eyclo hexyl) methane and decamethylene Diphenyl decamethylene dicarboxylate 54 0. 90 15 dicarboxylic acid. 67 Polyamide from NN bis (3 amino-n-propyl) pipera- {None (R V. 38) 3, 445 zine and adipic acid. Diphenyl adipat 75 (R V. 142) 3, 314 68 Poly meta xylylene adipamide None 0.78 93 Diphenyl adipate- 93 1. 26 69 Polyamide from 2,5 bis (beta amino ethyl) para {None 0.47 144 xylene and sebacic acid. Diphenyl sebaeate. 110 0. 96 17 70 Polyamino undecaneamide 53 Diphenyl adipate 53 13 22 1 In Example 67 the presence of basic tertiary nitrogen in the polyamide is shown by the high A.E.G. value both in the original polymer and in the chain extended polymer.

EXAMPLES 7175 of 66 nylon polymer of the following analysis, at a melt pool pressure of 760 mm. Hg and pool means residence T 1 shows the viscosit increase obtain usin abe 9 y ed g time of 20 minutes.

esters of the present invention in admixture with copolyamides. R.V. .5 A.E.G.54.5 C.E.G.-65.5

TABLE 9 Co-polyamides stirred at 285 C. for 15 mins. with diphenyl esters Amount, Analysis Ratio Equiv. Example Copolyamide A/B Diphenyl ester per 10g. I.V. (R.V.) Amine 71 Hexamethylene diammonium adipate (A) co-polymerized with 99 caprolactam (B). 28 7 66/6-- 47 86/1 77) 22 Dodecamethylene diainmonium (A) and hexamethylene diam- 75/25 None 0.71 53 monium (B) terephthalates copolymerized. 75/25 Diphenyl terephthalate..- 53 0.90 7 74 Hexamethylene (A) and metaxylylene (B) diammonium adipates /50 Non 0.91 86 oopolymerized. 50/50 Diphenyl adipate. 86 1.15 26 75 {Hexamethylene diamine (A) and N-(2 amino ethyD-piperazine (B). 85/15 None 0. 62 658 Neutralized with adipic acid and copolymerized 85/15 Diphenyl adipate 100 0.82 563 Nona-Example 75-see footnote 1 for Example 67 (Table 8).

EXAMPLE 76 When the melt pool pressure was reduced to 620 mm. Polymer chip with the following properties eelFtsiglute, the extruded yarn possessed the following prop- GHQ-75 R.V.-49.1 A.E.G.-51.5 C.E.G.-59.6

was dried in an oven and charged to the hopper of a An injection point was now fitted to the polymerization screw extruder. The throughout through the extruder was coil at a point 1.5 meters from the melt pool, the time for varied between 1.0 and 11.5 lb./hr. and after allowing polymer to flow from this point to the pool was 100 secconditions to equilibrate at each throughput, the extrudate onds. Dicresyl adipate was added at this point at a rate of was quenched in water and analyzed. A plot of RV. 60 g./hr. The melt pool pressure was 620 mm. and the against residence time is given in FIG. 1 (X). The resipolymer throughout was 7,250 g./h r. The resulting polydence times were estimated at each throughput by using mer possessed the following properties; POlYIners as tracers- R.V.-63.7 A.E.G.36.4 C.E.G.-63

Diphenyl adipate was then coated onto the dried chip at a loading of 49 gram equivalents DPA per/l0 gm. EXAMPLE 78 polymer and the above experiment was repeated. The re- A 66 nylon po1ymer prepared b normal autoclave Sults are also Shown in 1 lymerization techniques possessed the following prop- In order to investigate the affect of increased A.E.G. 7O erties level on the rate of RV. rise, a polymer of 45 R.V.,

A.E.G. and 62 C.E.G. was dried and coated with 65 gm.

equivs./10 gm. of diphenyl adipate. The above experiment was again repeated and the results are also shown in FIG. 1 (Z).

R.V.45.3 A.E.G.-66.4 C.E.G.-50 Copper 60 p.p.m. (acetate) Iodine-600 p.p.m. Boron22 p.p.m.

45.4 kg. of this polymer was tumble-mixed in a Gardner The physical properties of this yarn were:

Tenacity--9.3 g.p.d. Extension-43.5% TE -34 R.V.78 A.E.G.23 .5 C.E.G.68

The yarn was converted by conventional methods into greige cord construction two-fold 840/140 12Z/12S having a breaking load of 14.8 kg. When this cord was further processed using the conventional resorcinol-formaldehyde latex (R.F.L.) adhesive process, the breaking load of the dip dried hot stretched cord was 14.3 kg.

Cords produced by similar processes from polymer of analysis:

R.V.46 A.E.G.-51

p.p.m. (acetate) C.E.G.-70 Copper-66 Iodine-600 p.p.m.

giving yarn with properties:

without admixture of diphenyl adipate, possessed the following properties:

Tenacity8.8 Extension-13.5

Kg. Greige cord breaking load 13.0 R.F.L. dip dried hot stretched cord breaking load 12.8

EXAMPLE 79 The molecular weight distributions of two yarns were studied by coacervate extraction fractionation in phenol/ water at 70 C., J. Polymer Sci., 1962, 57, 357-372. Tire cord was used as a control for the other two yarns which were spun from tire cord polymers chip mixed with diphenyl adipate (DPA) powder to increase the spun yarn R.V. via chain extension (see Table Molecular weight distributions calculated from the fractionation data are shown in the form of Tungs analysis (I. Polymer Sci., 1956, 20, 495) in FIG. 2, which presents the experimental data in a linear form. The slope of the Tung analysis line b depends on the actual form of the molecular weight distribution and a value of b=1.89 has been found for undegraded linear 6.6 nylon polymers of R.V. 2090. For the tire cord and 85 R.V. yarn, experimental data was in excellent agreement with a slope of b=1.89; the Tung analysis of the higher R.V. yarn, althrough less well defined, still being in reasonable agreement with a line of the same slope.

The intercept a of Tungs analysis (b=1.89) is determined by the polymer molecular weight MW and the molecular weights calculated in this manner are shown in Table 10.

TABLE 10 Fractionation of T.C. and chain extended tire cord yarns The conclusion drawn from this work is that the yarn of high R.V. obtained via chain extension with DPA has essentially the same form of molecular weight distribution as the control T.C. yarn, but is of higher molecular weight. The conclusion is in agreement with theory which predicts that chain extension in 6.6 nylon takes place with no alteration in the shape of the molecular weight distribution.

What we claim is: I

1. A process for the production of a melt-spun fiber or filament from a synthetic linear melt-spinnable polyamide or copolyarnide made from dicarboxylic acid and diamine component and including free amine end groups obtained from said diamine component, said process comprising adding to and reacting with the synthetic linear polyamide or copolyamide in the molten state at least one diaryl ester of a dicarboxylic acid with a state amounts substantially stoichiometrically equivalent to the free amine end groups in said polyamide or copolyamide of number of 5 to 36 and having the carboxyl groups attached either to a single carbon atom, provided the other bonds of said carbon atom are connected to saturated aliphatic groups or form part of a saturated alicyclic structure, or attached to separate carbon atoms other than vicinalor eri-positioned carbon atoms; the aryl of said ester being monocyclic or dicyclic and said ester being added in a substantially stoichiometric amount with respect to said free amine end groups in said polyamide or copolyamide so as to increase the relative viscosity thereof by increasing the polymer chain length, and then melt-spinning the resulting melt into fiber or filament.

2. The process as claimed in claim 1 wherein said dicarboxylic acid of said ester is an aliphatic, cycloaliphatic, aromatic hydrocarbon or heterocyclic acid.

3. The process as claimed in claim 1 wherein said polyamide is polyhexamethylene adipamide.

4. The process as claimed in claim 1 wherein said di aryl ester is a diphenyl ester.

5. The process as claimed in claim 1 wherein said diaryl ester is a dicresyl ester.

6. The process as claimed in claim 1 wherein said diaryl ester is diphenyl adipate.

7. The process as claimed in claim 1 wherein said diaryl ester is dicresyl adipate.

8. The process as claimed in claim 1 wherein the time between adding the aryl ester to the melt and the solidification of the subsequently melt-spun product is such as to give substantially the optimum rise in relative viscosity of the spun product.

9. The process as claimed in claim 1 wherein said ester is coated onto said synthetic linear polyamide or copolyamide chip.

10. The process as claimed in claim 1 wherein said ester is added to said synthetic linear polyamide or copolyamide in the form of a master batch.

11. The process as claimed in claim 1 wherein said ester is added to a synthetic linear polyamide or copolyamide made in a continuous polymerization process.

(References on following page) Tung analysis Yarn References Cited UNITED STATES PATENTS HAROLD D. ANDERSON, Primary Exammer 'Walker 260-78 SC U.S. Cl. X.R.

Stamatoff 260-78 SC Schnegg et a. 2 0 7 SC 5 57-140 R; 260-18 N, 47 CZ, A, Fritz et a1 260-48 SC 6 F 

